The present disclosure relates generally to an integrated circuit having oxide films and, more specifically, to a plasma enhanced deposited oxide film.
One method of deposition is chemical vapor deposition (CVD), which includes plasma enhanced chemical vapor deposition (PECVD). The other method is thermal oxidation (TO). Various devices in an integrated circuit may be affected by the charge retention in the oxide film. Specifically, in metal oxide silicon transistors, once the biasing of the device is removed, the oxide may retain various levels of charge. This would affect the turn off and/or reactivation of the device. Historically, CVD oxide films have retained more charge than thermal oxidized films because the film includes dangling atoms, which are not fully bonded to each other (namely, incomplete reacted species).
This problem is addressed in the article “Development of a Fully Oxidized PECVD PSG Film,” Semiconductor International, p. 105 (August 2000). The suggested solution is to increase the N2O:SiH4 ratio and process pressure and using only high frequency RF power. The Si—O—Si bond peak wavelength in the infrared (IR) spectrum was 1091 cm−1 for the CVD oxide film compared to 1095 cm−1 for the TO oxide film.
The present disclosure has found that a modification of the PECVD process has substantially decreased the charge retention of the oxide and has improved the Si—O—Si bonding within the oxide so as to be more fully oxidized. This more fully oxidized bonding is reflected by an increase in the Si—O—Si bond peak wavelength in the IR spectrum. It is also capable of increased levels of doping, which have improved re-flow characteristics, as well as other characteristics.
The present method of forming a plasma enhanced deposited oxide film on a substrate includes introducing into a chamber containing the substrate silane gas and a dopant gas such as phosphine. The chamber is pressurized and energy is applied to create a plasma. The energy may be a dual frequency energy. The gas rates and pressure are selected to produce a plasma enhanced deposited oxide film on a substrate having a Si—O—Si bond peak absorbance in the IR spectrum of at least 1092 cm−1. The oxide film uniformity has a standard deviation of 0.7% maximum.
These and other aspects of the present disclosure will become apparent from the following detailed description of the disclosure, when considered in conjunction with accompanying drawings.